From 194bc1f48100a3b6fbd50d7a2218b594f0c564b6 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:36 +0300 Subject: fs, nfs: convert nfs4_lock_state.ls_count from atomic_t to refcount_t atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nfs4_lock_state.ls_count is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Anna Schumaker --- fs/nfs/nfs4state.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'fs/nfs/nfs4state.c') diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 0378e2257ca7..1887134d5231 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -825,7 +825,7 @@ __nfs4_find_lock_state(struct nfs4_state *state, ret = pos; } if (ret) - atomic_inc(&ret->ls_count); + refcount_inc(&ret->ls_count); return ret; } @@ -843,7 +843,7 @@ static struct nfs4_lock_state *nfs4_alloc_lock_state(struct nfs4_state *state, f if (lsp == NULL) return NULL; nfs4_init_seqid_counter(&lsp->ls_seqid); - atomic_set(&lsp->ls_count, 1); + refcount_set(&lsp->ls_count, 1); lsp->ls_state = state; lsp->ls_owner = fl_owner; lsp->ls_seqid.owner_id = ida_simple_get(&server->lockowner_id, 0, 0, GFP_NOFS); @@ -907,7 +907,7 @@ void nfs4_put_lock_state(struct nfs4_lock_state *lsp) if (lsp == NULL) return; state = lsp->ls_state; - if (!atomic_dec_and_lock(&lsp->ls_count, &state->state_lock)) + if (!refcount_dec_and_lock(&lsp->ls_count, &state->state_lock)) return; list_del(&lsp->ls_locks); if (list_empty(&state->lock_states)) @@ -927,7 +927,7 @@ static void nfs4_fl_copy_lock(struct file_lock *dst, struct file_lock *src) struct nfs4_lock_state *lsp = src->fl_u.nfs4_fl.owner; dst->fl_u.nfs4_fl.owner = lsp; - atomic_inc(&lsp->ls_count); + refcount_inc(&lsp->ls_count); } static void nfs4_fl_release_lock(struct file_lock *fl) -- cgit